Ancient Haplotypes at the 15q24.2 Microdeletion Region Are Linked to Brain Expression of MAN2C1 and Children's Intelligence

15q24 Duplication: A Case Report of Neurodevelopmental Delay

Chromosomal rearrangements are structural anomalies that affect chromosomal architecture and can impact gene expression, genomic imprinting, or even generate de novo gene fusions, as seen in hematological chromosomal aberrations. Chromosomal rearrangements can be associated with syndromes causing neurodevelopmental delay, autism spectrum disorder, and variable dysmorphic features. This article presents the clinical and molecular characteristics of a 2-year-old male child with neurodevelopmental delay who was diagnosed with a chromosomal rearrangement due to a 15q24 duplication (dup15q24). The 15q24 locus presents controversy between the phenotype associated with duplication and deletion, thus posing a challenge in differential diagnosis for both. The phenotypes of autism spectrum disorder and pediatric patients with language delay should be evaluated by a multidisciplinary team comprising genetics, pediatrics, and pediatric neurology to shorten the diagnostic odyssey for patients with rare diseases and to impact the quality of life of the patient and their family.

Discovery of eQTL Alleles Associated with Autism Spectrum Disorder: A Case-Control Study

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disorder characterized by challenges in social communication as well as repetitive or restrictive behaviors. Many genetic associations with ASD have been identified, but most associations occur in a fraction of the ASD population. Here, we searched for eQTL-associated DNA variants with significantly different allele distributions between ASD-affected and control. Thirty significant DNA variants associated with 174 tissue-specific eQTLs from ASD individuals in the SPARK project were identified. Several significant variants fell within brain-specific regulatory regions or had been associated with a significant change in gene expression in the brain. These eQTLs are a new class of biomarkers that could control the myriad of brain and non-brain phenotypic traits seen in ASD-affected individuals.

Impaired catabolism of free oligosaccharides due to MAN2C1 variants causes a neurodevelopmental disorder

Free oligosaccharides (fOSs) are soluble oligosaccharide species generated during N-glycosylation of proteins. Although little is known about fOS metabolism, the recent identification of NGLY1 deficiency, a congenital disorder of deglycosylation (CDDG) caused by loss of function of an enzyme involved in fOS metabolism, has elicited increased interest in fOS processing. The catabolism of fOSs has been linked to the activity of a specific cytosolic mannosidase, MAN2C1, which cleaves α1,2-, α1,3-, and α1,6-mannose residues. In this study, we report the clinical, biochemical, and molecular features of six individuals, including two fetuses, with bi-allelic pathogenic variants in MAN2C1; the individuals are from four different families. These individuals exhibit dysmorphic facial features, congenital anomalies such as tongue hamartoma, variable degrees of intellectual disability, and brain anomalies including polymicrogyria, interhemispheric cysts, hypothalamic hamartoma, callosal anomalies, and hypoplasia of brainstem and cerebellar vermis. Complementation experiments with isogenic MAN2C1-KO HAP1 cells confirm the pathogenicity of three of the identified MAN2C1 variants. We further demonstrate that MAN2C1 variants lead to accumulation and delay in the processing of fOSs in proband-derived cells. These results emphasize the involvement of MAN2C1 in human neurodevelopmental disease and the importance of fOS catabolism.